Muffler

ABSTRACT

A muffler is disposed in an exhaust pipe extending from an internal combustion engine along a bottom side of a vehicle. The muffler includes a cylindrical outer shell having a pair of openings defined at opposing axial ends of the outer shell and a pair of outer plates each secured to the corresponding one of the opposing ends of the outer shell. The muffler has an interior defined by the outer plates and the outer shell. The muffler further includes an inlet pipe and an outlet pipe each supported by the corresponding one of the outer plates and extending in the interior of the muffler. Each of the inlet and outlet pipes has a curved portion. The curved portion is accommodated in the interior of the muffler. Accordingly, the muffler is configured relatively simple and has improved durability.

BACKGROUND OF THE INVENTION

The present invention relates to mufflers for suppressing a noise caused by exhaust gas of a vehicle engine.

For example, Japanese Laid-Open Patent Publication No. 57-113919 describes this type of muffler, as illustrated in FIG. 7. With reference to the drawing, a generally used, conventional muffler, such as the one described in the aforementioned publication, will hereafter be explained.

As shown in FIG. 7, a muffler 50 is deployed at a bottom side of a vehicle body and between exhaust pipes EX1, EX2. More specifically, the muffler 50 includes an outer shell 53 and a pair of outer plates 51, 52, which are securely supported by the outer shell 53. The muffler 50 is connected to the exhaust pipes EX1 through the outer plate 51 and to the exhaust pipe EX2 through the outer plate 52. Exhaust gas is introduced to the interior of the muffler 50 through the exhaust pipes EX1 (the inlet pipes) and discharged to the exterior through the exhaust pipe EX2 (the outlet pipe). While flowing through the muffler 50, the energy of the exhaust gas is reduced such that a noise caused by the exhaust gas is suppressed.

Since the muffler 50 is normally installed along a portion of the bottom side of the vehicle body, the installing position of the muffler 50 is limited. The exhaust pipes EX1, EX2 of the engine thus must be curved at a plurality of positions as connected to the muffler 50. Normally, curved portions R of the exhaust pipes EX1, EX2 are formed in the immediate vicinity of the muffler 50.

The rigidity of each of the curved portions R is relatively low as compared to the remainder of the corresponding exhaust pipes EX1, EX2. Thus, when the engine or vehicle body vibrates, the external force acting on the exhaust pipes EX1, EX2 causes relatively great deformation (vibration) in the curved portions R, as compared to the remainder of the corresponding exhaust pipes EX1, EX2. As aforementioned, the curved portions R are located in the immediate vicinity of the muffler 50. Accordingly, for example, the vibration of the curved portion R of each exhaust pipe EX1 acts directly on a connecting portion P of the exhaust pipe EX1 with the outer plate 51 of the muffler 50 as moment E, as illustrated in FIG. 8, which is an enlarged view showing the section D of FIG. 7. As is clear from FIG. 8, the moment E acts to deform the connecting portion P, thus lowering the durability of the connecting portion P of the exhaust pipe EX1, as well as that of the muffler 50. A connecting portion of the exhaust pipe EX2 with the outer plate 52 of the muffler 50 (FIG. 7) is also affected in a similar manner by the vibration of the vehicle engine or body.

In order to avoid the disadvantage, various solutions have been proposed. For example, the outer plates 51, 52 of the muffler 50 may be formed of a relatively thick material. Alternatively, a reinforcing member or damper may be added for suppressing the deformation (the vibration) of each curved portion R. However, the solutions may increase the weight of the muffler 50 or complicate the exhaust system configuration and thus are not significantly efficient.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a simply configured muffler capable of preferably suppressing lowering of durability, which is otherwise caused by vibration of a curved portion of an exhaust pipe.

To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the invention provides a muffler for suppressing a noise caused by exhaust gas of an internal combustion engine of a vehicle. The muffler is disposed in an exhaust pipe extending from the engine along a bottom side of the vehicle. The muffler includes a cylindrical outer shell having a pair of openings defined at opposing axial ends of the outer shell, and a pair of outer plates each secured to the corresponding one of the opposing ends of the outer shell. The exhaust pipe is connected to the outer plates and has a curved portion in the vicinity of at least one of the connecting portions of the exhaust pipe with the outer plates. The curved portion is accommodated in the interior of the muffler defined by the outer plates and the outer shell.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a plan view showing an exhaust system of a vehicle to which an embodiment of the present invention is applied;

FIG. 2 is a partially cross-sectional, plan view showing the interior of a muffler of the illustrated embodiment;

FIG. 3 is a front view showing the muffler of FIG. 2 as viewed from the direction indicated by arrow A;

FIG. 4 is a front view showing the muffler of FIG. 2 as viewed from the direction indicated by arrow B;

FIG. 5 is an enlarged cross-sectional view showing the section C of FIG. 2;

FIG. 6 is a plan view showing arrangement of exhaust pipes in the vicinity of the muffler;

FIG. 7 is a plan view showing a conventional exhaust system configuration of a vehicle; and

FIG. 8 is a view schematically showing moment acting on a connecting portion of an exhaust pipe with a conventional muffler.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described.

First, an exhaust system configuration of a vehicle to which a muffler 20 of the present invention is applied will be explained with reference to FIG. 1.

As shown in the drawing, the muffler 20 is disposed in an exhaust pipe extending from an internal combustion engine along a bottom side of a vehicle body, like the conventional muffler 50 of FIG. 7. The exhaust pipe includes a pair of exhaust pipes (first pipe sections) 12 extending from the engine to the muffler 20 and an exhaust pipe (a second pipe section) 14 extending from the muffler 20 to the exterior.

The structure of the muffler 20 will hereafter be explained in detail referring to FIG. 2.

As illustrated in the drawing, the muffler 20 includes inlet pipes 22, an outlet pipe 24, a pair of outer plates 26, 28, and an outer shell 30. Each of the inlet pipes 22 is connected to the corresponding one of the exhaust pipes 12. The outlet pipe 24 is connected to the exhaust pipe 14. The outer plate 26 is connected to the inlet pipes 22 and the outer plate 28 is connected to the outlet pipe 24. The outer shell 33 supports the outer plates 26, 28.

In other words, each inlet pipe 22 is connected to the corresponding exhaust pipe 12 (FIG. 1) and thus forms a section of the exhaust pipe 12. More specifically, each exhaust pipe 12 includes the corresponding inlet pipe 22, which is an inner pipe section disposed in the interior of the muffler 20, and an outer pipe section arranged in the exterior of the muffler 20 and connected to the inner pipe section. Like the inlet pipes 22, the outlet pipe 24 is connected to the exhaust pipe 14 (FIG. 1) and thus forms a section of the exhaust pipe 14. More specifically, the exhaust pipe 14 includes the outlet pipe 24, which is an inner pipe section disposed in the interior of the muffler 20, and an outer pipe section arranged in the exterior of the muffler 20 and connected to the inner pipe section. The outer plate 26 is connected to a portion of each of the inlet pipes 22 and the outer plate 28 is connected to a portion of the outlet pipe 24. The outer shell 30 is formed like a cylinder having a substantially oval cross-sectional shape. Each of the outer plates 26, 28 and the outer shell 30 is formed by piling a pair of metal thin plates together.

In the illustrated embodiment, a plurality of separators 32 are formed in the interior of the muffler 20, the space defined by the outer plates 26, 28 and the outer shell 30. The separators 32 thus define a plurality of resonance chambers in the interior of the muffler 20 along the axial direction of the muffler 20.

Each of the outer plates 26, 28 is formed in a manner expanded in the axial direction of the muffler 20, as shaped like a substantially spherical, or, more specifically, oval surface as a whole. As compared to the case in which each outer plate 26, 28 is formed as a flat surface, the outer plate 26, 28 of the illustrated embodiment has a relatively large heat dissipating surface area, thus improving the noise suppressing performance of the muffler 20. Further, as compared to the case in which each outer plate 26, 28 forms a flat surface, the wind received by the outer plates 26, 28 when the vehicle is moving is deflected more smoothly along the outer wall of the muffler 20, thus decreasing the aerodynamic drag acting on the muffler 20. In addition, since the inlet and outlet pipes 22, 24 are supported by the corresponding outer plates 26, 28 having improved surface rigidity, the rigidity of the muffler 20 as a whole is increased, thus enhancing the durability of the muffler 20.

The outer plate 26 has a plurality of projections 34 each projected outward from the muffler 20. Similarly, the outer plate 28 has a plurality of projections 36 each projected outward from the muffler 20. As illustrated in the front views of FIGS. 3 and 4, each of the projections 34, 36 is formed in an elongated shape and functions as a reinforcing rib. This structure further improves the surface rigidity of each outer plate 26, 28. Further, in addition to the outer plates 26, 28 that are shaped in the expanded manner, the projections 34, 36 increase the surface area, or the heat dissipating surface area, of the corresponding outer plates 26, 28. This enhances the exhaust gas cooling performance of the muffler 20, as well as the noise suppressing performance of the muffler 20.

With reference to FIG. 2, each of the inlet pipes 22 is connected to the outer plate 26 as passed through the outer plate 26. Likewise, the outlet pipe 24 is connected to the outer plate 28 as passed through the outer plate 28. More specifically, a connecting portion of each inlet pipe 22 with the outer plate 26 (the section C of FIG. 2) is shown in the enlarged view of FIG. 5, by way of example. That is, a through hole 38 extends through each of the outer plates 26, 28. A burring portion 40 is formed through burring along the periphery of each of the through holes 38. Each of the inlet and outlet pipes 22, 24 is thus passed through the corresponding one of the through holes 38 of the outer plate 26, 28 and welded to the burring portion 40. The inlet and outlet pipes 22, 24 are thus secured to the corresponding outer plates 26, 28. In the interior of the muffler 20, the inlet pipes 22 and the outlet pipes 24 are secured to the corresponding separators 32 as passed through the separators 32.

Further referring to FIG. 2, each of the inlet pipes 22 includes a curved portion R in the vicinity of the connecting portion with the outer plate 26. The extending direction of each inlet pipe 22 is changed at the corresponding curved portion R. Similarly, the outlet pipe 24 includes a curved portion R in the vicinity of the connecting portion with the outer plate 28. The extending direction of the outlet pipe 24 is changed at the curved portion R. In the illustrated embodiment, each of the curved portions R is formed in the muffler 20 as received in the space defined by the expanded portion of the corresponding outer plate 26, 28.

With reference to FIG. 1 or FIG. 6, an enlarged view showing a section of FIG. 1, this structure makes it unnecessary to form a curved portion in either of the exhaust pipes 12, 14 corresponding to the exterior of the muffler 20, in the vicinity of the corresponding outer plate 26, 28. Further, the configuration of the illustrated embodiment saves the space defined in the muffler 20 efficiently. Also, in the muffler 20, the sections of the inlet pipes 22 (the exhaust pipes 12) and the section of the outlet pipe 24 (the exhaust pipe 14), each including the corresponding curved portion R (see FIG. 2), are supported by a plurality of portions of the muffler 20 corresponding to the separators 32. This structure suppresses deformation and vibration occurring in the curved portions R, which are received in the interior of the muffler 20. Accordingly, simply by accommodating the curved portions R in the interior of the muffler 20, the durability of the muffler 20 of the illustrated embodiment is improved. Further, among a plurality of curved portions formed in each of the exhaust pipes 12, 14, some of the curved portions, the curved portions R, are received in the interior of the muffler 20 This suppresses deformation of the exhaust pipes 12, 14, as well as vibration of the exhaust system as a whole.

In addition, as is often the case with a conventional muffler, it may be possible to bond an outer shell and outer plates together through “caulking”. More specifically, the outer plates are fitted in the outer shell, which is originally shaped as a cylinder. Each of the outer plates is then securely pressed by a mold at the entire circumference for preventing the outer plates from separating from the outer shall. The outer shell and the outer plates are thus subjected to the caulking. Accordingly, the portion of each outer plate pressed by the mold must be shaped as a flat surface.

However, if the caulking is employed for forming the muffler 20 of the illustrated embodiment, the inlet pipes 22 and the outlet pipe 24 may interfere with the mold, making it difficult to bond the outer shell 30 and the outer plates 26, 28 together. Also, since each outer plate 26, 28 is shaped as a substantially spherical, oval surface, it may be difficult to provide a flat surface portion for being pressed by the mold. In this case, the pressing may not be accomplished appropriately. Further, if each of the outer plates 26, 28 includes the flat surface portion, vibration of the outer plate 26, 28 as a whole, or that of the muffler 20, may be caused by vibration of the flat portion. The rigidity of the muffler 20 is thus lowered.

To avoid this, the illustrated embodiment employs laser welding for bonding the outer shell 30 and the outer plates 26, 28 together. The laser welding is accomplished easily and appropriately simply by securely holding the outer plates 26, 28 with respect to the outer shell 30 using a mold such that the outer plates 26, 28 are positioned accurately. It is thus unnecessary to press the entire circumference of each outer plate 26, 28 against the outer shell 30. Further, the position for applying the mold in each outer plate 26, 28 can be selected such that the mold is not interfered by the inlet pipes 22 or the outlet pipes 24.

It is thus possible to form the muffler 20 relatively easily while maintaining the bonding strength between the outer shell 30 and the outer plates 26, 28 at a relatively high level. Further, the extending direction of each of the inlet pipes 22 (the exhaust pipes 12) and the outlet pipe 24 (the exhaust pipe 14) outside the muffler 20 may be selected with less restrictions. Also, it is unnecessary to form a flat surface portion in each outer plate 26, 28 for bonding the outer plates 26, 28 and the outer shell 30 together. The outer plates 26, 28 are thus assembled with the outer shell 30 relatively easily.

In the following, a procedure for assembling the muffler 20 will be explained by way of example. The muffler 20 of the illustrated embodiment is assembled in accordance with the following steps 1 to 3.

<Step 1> The inlet pipes 22 and the outlet pipe 24 are secured to the separators 32. More specifically, each of the inlet pipes 22 is configured by a bent portion 22 a and a straight portion 22 b. The bent portion 22 a includes the corresponding curved portion R and is located closer to the outer plate 26. The straight portion 22 b is located inward in the muffler 20. In Step 1, only the straight portions 22 b of the inlet pipes 22 are secured to the separators 32.

<Step 2> Two metal sheets that are piled together are wound around the separators 32 to which the inlet and outlet pipes 22, 24 are secured. The ends of the metal sheets are then joined together through welding, such that the outer shell 30 is completed.

<Step 3> An end of the bent portion 22 a of each inlet pipe 22 is fitted in the corresponding end of the straight portion 22 b, such that the bent portion 22 a and the straight portion 22 b form a single pipe. The bent portion 22 a of each inlet pipe 22 is then connected to the outer plate 26. In this state, the outer plates 26, 28 are fitted in a pair of opposing ends of the outer shell 30. The outer plates 26, 28 and the outer shell 30 are then bonded together through welding.

The illustrated embodiment has the following advantages.

(1) The connecting portion of each inlet pipe 22 with the outer plate 26 and the connecting portion of the outlet pipe 24 with the outer plate 28 are each prevented from being affected directly by the vibration of the corresponding curved portion R, which is applied to the connecting portion as the moment acting to deform the connecting portion. Accordingly, the durability of the muffler 20 of the illustrated embodiment is improved simply by receiving the curved portions R in the interior of the muffler 20.

(2) In the illustrated embodiment, the strength of each outer plate 26, 28 is increased by shaping the outer plate 26, 28 in an expanding manner. The volume and heat dissipating surface area of the muffler 20 is also increased, and the noise caused by exhaust gas is suppressed further effectively. Further, the curved portion R of each of the inlet and outlet pipes 22, 24 is accommodated in the space defined by the expanded portion of the corresponding outer plate 26, 28, such that the space in the muffler 20 is saved efficiently. Also, when the vehicle is moving, the wind received by the muffler 20 is easily deflected along the outer wall of the muffler 20 by following the expanded shape of each outer plate 26, 28. This structure reduces the aerodynamic drag acting on the muffler 20, thus lowering the air flow resistance when the vehicle is moving.

(3) Since each of the outer plates 26, 28 is shaped as a substantially oval surface in the illustrated embodiment, the surface rigidity of each outer plate 26, 28 supporting the inlet or outlet pipes 26, 28 is relatively large. The rigidity of the muffler 20 is thus enhanced as a whole, such that the durability of the muffler 20 is improved further preferably.

(4) Each outer plate 26, 28 is provided with the burring portion(s) 40 for supporting the corresponding inlet or outlet pipes 22, 24. This structure makes it possible to support the inlet and outlet pipes 22, 24 by the corresponding outer plates 26, 28 without providing a flat surface portion in the outer plates 26, 28. The vibration of the muffler 20 is thus suppressed in a preferable manner.

(5) In the illustrated embodiment, the projections (the reinforcing ribs) 34, 36 are formed respectively in the outer plates 26, 28. This structure further improves the surface rigidity of each outer plate 26, 28 and increases the heat dissipating surface area of the outer plate 26, 28.

(6) In the illustrated embodiment, the outer plates 26, 28 and the outer shell 30 are bonded together through laser welding. This makes it easy to position the outer plates 26, 28 with respect to the outer shell 30 and maintain the bonding strength between the outer plates 26, 28 and the outer shell 30 at a relatively high level. Particularly, since the muffler 20 of the illustrated embodiment accommodates the curved portions R in the interior, the outer plates 26, 28 are relatively difficult to securely assemble with the outer shell 30. However, as long as the laser welding is employed, the problem is solved preferably. Further, as compared to the case in which the outer plates 26, 28 and the outer shell 30 are bonded together through, for example, caulking, the weight of the muffler 20 of the illustrated embodiment is relatively light.

The present invention may be embodied in the following modified forms.

Although each of the projections 34, 36 is formed in an elongated shape in the illustrated embodiment, the shape of each projection 34, 36 may be modified as needed.

Instead of, or in addition to, the projections 34, 36, a plurality of recesses recessed inward with respect to the muffler 20 may be formed in the outer plates 26, 28. Since the recesses each function as a reinforcing rib, this structure also increases the surface rigidity of each outer plate 26, 28. Further, the recesses increase the heat dissipating surface area of each outer plate 26, 28.

Alternatively, the projections 34, 36 or the recesses may be eliminated from the outer plates 26, 28, as long as the required surface rigidity and heat dissipating surface area are reliably obtained in the outer plates 26, 28.

In the illustrated embodiment, the burring portions 40 may be omitted or replaced by other types of flanges, as long as the inlet and outlet pipes 22, 24 are held in a secure state appropriately.

If the space in the muffler 20 is saved sufficiently in the illustrated embodiment, each curved portion R does not necessarily have to be accommodated in the space defined by the expanded portion of the corresponding outer plate 26, 28. As long as the curved portions R are located in the interior of the muffler 20, similar advantages to those of the illustrated embodiment may be obtained.

Alternatively, only some of the curved portions R may be accommodated in the interior of the muffler 20. This structure also prevents the connecting portion of each inlet pipe 22 with the outer plate 26 and the connecting portion of the outlet pipe 24 with the outer plate 28 from being affected directly by the vibration of the corresponding curved portion R, which is applied to such connecting portion as the moment acting to deform the connecting portion.

In the illustrated embodiment, only one of the outer plates 26, 28 may be formed in an expanded shape along the axial direction of the muffler 20.

In the illustrated embodiment, each of the outer plates 26, 28 is shaped as a substantially oval surface. However, a portion or the entire part of each outer plate 26, 28 may be shaped as a cone-like surface or a substantially cone-like surface. In other words, as long as the outer plates 26, 28 are each shaped as a substantially spherical surface, the surface rigidity of each outer plate 26, 28 is enhanced as compared to the case in which the outer plates 26, 28 are formed as flat surfaces.

In the illustrated embodiment, the outer shell 30 and the outer plates 26, 28 are bonded together through laser welding. However, bonding of the outer shell 30 and the outer plates 26, 28 may be accomplished through a similar but different type of welding, other than the laser type.

The present invention may be applied to a muffler having a single inlet pipe 22 or a muffler having a plurality of outlet pipes 24.

The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. 

1. A muffler for suppressing a noise caused by exhaust gas of an internal combustion engine of a vehicle, the muffler being disposed in an exhaust pipe extending from the engine along a bottom side of the vehicle, the muffler comprising: a cylindrical outer shell having a pair of openings defined at opposing axial ends of the outer shell; and a pair of outer plates each secured to the corresponding one of the opposing ends of the outer shell, the exhaust pipe being connected to the outer plates and having a curved portion in the vicinity of at least one of the connecting portions of the exhaust pipe with the outer plates, the curved portion being accommodated in the interior of the muffler defined by the outer plates and the outer shell.
 2. The muffler according to claim 1, wherein at least one of the outer plates is expanded outward in the axial direction of the outer shell, and wherein the curved portion is accommodated in a section of the interior of the muffler defined by the expanded portion of the outer plate.
 3. The muffler according to claim 2, wherein the outer plate is expanded like a substantially spherical surface.
 4. The muffler according to claim 2, wherein the expanded outer plate includes a burring for supporting the exhaust pipe.
 5. The muffler according to claim 2, wherein a reinforcing rib is formed on a surface of the expanded outer plate.
 6. The muffler according to claim 1, wherein each of the outer plates is bonded with the outer shell through laser welding.
 7. The muffler according to claim 1, wherein the exhaust pipe includes an inner pipe section extending in the interior of the muffler and having the curved portion and an outer pipe section extending in the exterior of the muffler and connected to the inner pipe section, the inner pipe section being incorporated in the muffler for forming a portion of the muffler.
 8. The muffler according to claim 7, wherein a separator is provided in the muffler for defining a plurality of resonance chambers in the interior of the muffler, and wherein the inner pipe section is supported by one of the outer plates and the separator such that the curved portion is arranged between the outer plate and the separator.
 9. The muffler according to claim 1, wherein the exhaust pipe includes a first pipe section extending between the engine and one of the outer plates and a second pipe section extending from the other one of the outer plates to the exterior of the muffler, and wherein the curved portion is one of curved portions each formed in the corresponding one of the first and second pipe sections, the curved portions of the first and second pipe sections being accommodated in the interior of the muffler.
 10. A muffler for suppressing a noise caused by exhaust gas of an internal combustion engine of a vehicle, the muffler being disposed in an exhaust pipe extending from the engine along a bottom side of the vehicle, the exhaust pipe including a first pipe section extending between the engine and the muffler and a second pipe section extending from the muffler to the exterior, the muffler comprising: a cylindrical outer shell having a pair of openings defined at opposing axial ends of the outer shell; first and second outer plates each secured to the corresponding one of the opposing ends of the outer shell, the muffler having an interior defined by the outer plates and the outer shell; a first inner pipe supported by the first outer plate and extending in the interior of the muffler, the first inner pipe having an end connected to the first pipe section in the exterior of the muffler; and a second inner pipe supported by the second outer plate and extending in the interior of the muffler, the second inner pipe having an end connected to the second pipe section in the exterior of the muffler, wherein at least one of the first and second inner pipes includes a curved portion in the vicinity of the portion of the inner pipe supported by the corresponding outer plate, the curved portion being accommodated in the interior of the muffler.
 11. The muffler according to claim 10, wherein the outer plate that supports the inner pipe having the curved portion is expanded outward in the axial direction of the outer shell, the curved portion being accommodated in a section of the interior of the muffler defined by the expanded portion of the outer plate.
 12. The muffler according to claim 11, wherein the outer plate is expanded like a substantially spherical surface.
 13. The muffler according to claim 11, wherein the expanded outer plate includes a burring for supporting the corresponding inner pipe.
 14. The muffler according to claim 11, wherein a reinforcing rib is formed on a surface of the expanded outer plate.
 15. The muffler according to claim 10, wherein each of the first and second outer plates is bonded with the outer shell through laser welding.
 16. The muffler according to claim 10, wherein a separator is provided in the muffler for defining a plurality of resonance chambers in the interior of the muffler, and wherein the inner pipe having the curved portion is supported by the corresponding outer plate and the separator such that the curved portion is arranged between the outer plate and the separator. 